Bitumen is a versatile material that is widely used in civil engineering. One use of bitumen is as an adhesive for repairing cracks in buildings and road surfaces, and as a joint sealant. When used as an adhesive, it is generally necessary to heat the bitumen to a temperature where it becomes workable before it can be applied. However, for certain applications this is inconvenient and bitumen compositions have been developed which are cold-applicable, i.e. they may be applied as an adhesive without the need for heating. One such composition is described in EP-A 37136.
The compositions of EP-A 37136 are cold-applicable adhesives that comprise bitumen, an elastomer, and a lithium salt of a fatty acid. The lithium salt acts as a thixotropic agent, causing the composition to harden after application. The compositions have the ability to bond to many substrates in cold and damp conditions and are widely used as sealants on metal, concrete and brickwork; in the roofing industry; and in hydraulic applications, for example as sealants for canal linings or waterproofing cement concrete dams.
To facilitate application, the compositions of EP-A 37136 may further comprise an aromatic hydrocarbon solvent (e.g. benzene, toluene, xylene etc) or a halogenated hydrocarbon solvent (e.g. dichloromethane or 1,1,1,-trichloroethane). These solvents evaporate after application, causing the composition to harden or cure.
To date, the only solvents considered suitable for use in cold-applicable compositions such as those described in EP-A 37136 are aromatic hydrocarbon solvents or halogenated solvents; 1,1,1,-trichloroethane being especially preferred. However, in recent years it has been found that aromatic hydrocarbon and halogenated solvents are harmful to the environment and may have detrimental effects on human health. Therefore, it would be advantageous if there was a means of replacing these solvents in cold-applicable bituminous adhesives.